/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */


package org.apache.flink.runtime.testutils.recordutils;

import org.apache.flink.api.common.typeutils.TypeComparator;
import org.apache.flink.api.common.typeutils.TypePairComparator;
import org.apache.flink.api.common.typeutils.TypePairComparatorFactory;
import org.apache.flink.types.Record;
import org.apache.flink.types.Value;

/**
 * A factory for a {@link TypePairComparator} for {@link Record}. The comparator uses a subset of
 * the fields for the comparison. That subset of fields (positions and types) is read from the
 * supplied configuration.
 */
public class RecordPairComparatorFactory implements TypePairComparatorFactory<Record, Record> {
	
	private static final RecordPairComparatorFactory INSTANCE = new RecordPairComparatorFactory();
	
	/**
	 * Gets an instance of the comparator factory. The instance is shared, since the factory is a
	 * stateless class. 
	 * 
	 * @return An instance of the comparator factory.
	 */
	public static final RecordPairComparatorFactory get() {
		return INSTANCE;
	}

	@Override
	public TypePairComparator<Record, Record> createComparator12(
			TypeComparator<Record> comparator1,	TypeComparator<Record> comparator2)
	{
		if (!(comparator1 instanceof RecordComparator && comparator2 instanceof RecordComparator)) {
			throw new IllegalArgumentException("Cannot instantiate pair comparator from the given comparators.");
		}
		final RecordComparator prc1 = (RecordComparator) comparator1;
		final RecordComparator prc2 = (RecordComparator) comparator2;
		
		final int[] pos1 = prc1.getKeyPositions();
		final int[] pos2 = prc2.getKeyPositions();
		
		final Class<? extends Value>[] types1 = prc1.getKeyTypes();
		final Class<? extends Value>[] types2 = prc2.getKeyTypes();
		
		checkComparators(pos1, pos2, types1, types2);
		
		return new RecordPairComparator(pos1, pos2, types1);
	}

	@Override
	public TypePairComparator<Record, Record> createComparator21(
		TypeComparator<Record> comparator1,	TypeComparator<Record> comparator2)
	{
		if (!(comparator1 instanceof RecordComparator && comparator2 instanceof RecordComparator)) {
			throw new IllegalArgumentException("Cannot instantiate pair comparator from the given comparators.");
		}
		final RecordComparator prc1 = (RecordComparator) comparator1;
		final RecordComparator prc2 = (RecordComparator) comparator2;
		
		final int[] pos1 = prc1.getKeyPositions();
		final int[] pos2 = prc2.getKeyPositions();
		
		final Class<? extends Value>[] types1 = prc1.getKeyTypes();
		final Class<? extends Value>[] types2 = prc2.getKeyTypes();
		
		checkComparators(pos1, pos2, types1, types2);
		
		return new RecordPairComparator(pos2, pos1, types1);
	}
	
	// --------------------------------------------------------------------------------------------

	private static final void checkComparators(int[] pos1, int[] pos2, 
							Class<? extends Value>[] types1, Class<? extends Value>[] types2)
	{
		if (pos1.length != pos2.length || types1.length != types2.length) {
			throw new IllegalArgumentException(
				"The given pair of RecordComparators does not operate on the same number of fields.");
		}
		for (int i = 0; i < types1.length; i++) {
			if (!types1[i].equals(types2[i])) {
				throw new IllegalArgumentException(
				"The given pair of RecordComparators does not operates on different data types.");
			}
		}
	}
}